title: Oligomerization and higher-order assembly contribute to sub-cellular localization of a bacterial scaffold.
abstract: In Caulobacter crescentus, the PopZ polar scaffold protein supports asymmetric cell division by recruiting distinct sets of binding partners to opposite cell poles. To understand how polar organizing centres are established by PopZ, we investigated a set of mutated PopZ proteins for defects in sub-cellular localization and recruitment activity. We identified a domain within the C-terminal 76 amino acids that is necessary and sufficient for accumulation as a single subcellular focus, a domain within the N-terminal 23 amino acids that is necessary for bipolar targeting, and a linker domain between these localization determinants that tolerates large variation. Mutations that inhibited dynamic PopZ localization inhibited the recruitment of other factors to cell poles. Mutations in the C-terminal domain also blocked discrete steps in the assembly of higher-order structures. Biophysical analysis of purified wild type and assembly defective mutant proteins indicates that PopZ self-associates into an elongated trimer, which readily forms a dimer of trimers through lateral contact. The final six amino acids of PopZ are necessary for connecting the hexamers into filaments, and these structures are important for sub-cellular localization. Thus, PopZ undergoes multiple orders of self-assembly, and the formation of an interconnected superstructure is a key feature of polar organization in Caulobacter.
authors.affiliation: Department of Developmental Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA.
authors.forename: Grant R
authors.initials: GR
authors.lastname: Bowman
authors.forename: Adam M
authors.initials: AM
authors.lastname: Perez
authors.forename: Jerod L
authors.initials: JL
authors.lastname: Ptacin
authors.forename: Eseosa
authors.initials: E
authors.lastname: Ighodaro
authors.forename: Ewa
authors.initials: E
authors.lastname: Folta-Stogniew
authors.forename: Luis R
authors.initials: LR
authors.lastname: Comolli
authors.forename: Lucy
authors.initials: L
authors.lastname: Shapiro
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D016935:Caulobacter crescentus / Q000737:chemistry* / Q000378:metabolism; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D002876:Chromosomes, Bacterial / Q000378:metabolism; D002942:Circular Dichroism; D017354:Point Mutation; D011487:Protein Conformation; D017510:Protein Folding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary
chemical_list: D001426:Bacterial Proteins; C052883:chromosome partition proteins, bacterial